Citethis:NewJ.Chem.,2011,35 ,724737 PAPERsuprachem.photonics.ru › pdf › NewJ.Chem.,2011,35,724-737.pdf · 724 NewJ.Chem., 2011,35 , 724737 This journal is c The Royal Society

724 New J. Chem., 2011, 35, 724–737 This journal is c The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2011

Cite this: New J. Chem., 2011, 35, 724–737

Controlled self-assembly of bis(crown)stilbenes into unusual bis-sandwich

complexes: structure and stereoselective [2+2] photocycloadditionw

Sergey P. Gromov,*aArtem I. Vedernikov,

aNatalia A. Lobova,

a

Lyudmila G. Kuz’mina,bStepan S. Basok,

cYuri A. Strelenko,

d

Michael V. Alfimovaand Judith A. K. Howard

e

Received (in Montpellier, France) 11th October 2010, Accepted 30th November 2010

DOI: 10.1039/c0nj00780c

It was shown by 1H NMR spectroscopy that symmetrical bis(crown)stilbenes (L) and small alkali

and alkaline-earth metal cations form 1(L) : 1(Mm+) and 1(L) : 2(Mm+) complexes in MeCN

solutions. In the case of large or hydrated metal cations such as Cs+, Rb+, K+, Ba2+, Sr2+,

[Ca(H2O)x]2+ and stilbenes with a small crown-ether cavity as compared with the metal cation

size, stable bis-sandwich complexes 2(L) : 2(Mm+) can also be formed. A stable

bis-pseudosandwich 2 : 2 complex is also produced from bis(18-crown-6)stilbene with the

propanediammonium ion. The effect of the crown-ether size and the cation size and nature on the

route of stilbene phototransformation and product composition was elucidated. The

bis-(pseudo)sandwich complexes undergo effective stereoselective [2+2] photocycloaddition giving

mainly rctt isomers of new 1,2,3,4-tetracrown cyclobutanes. The structures of complexes of

bis(crown)stilbenes and obtained cyclobutanes were confirmed by X-ray diffraction.

Introduction

Stilbenes and their analogues containing a 1,2-di(aryl/hetaryl)-

ethylene structural fragment are the subjects of numerous

studies as they possess remarkable spectral fluorescence

and photochemical properties such as the ability to undergo

reversible E/Z isomerization, electrocyclization, and [2+2]

photocycloaddition (PCA).1 These properties were used to

design optoelectric media and obtain multiphoton absorption

materials for lasers and proposed for optical information

recording and storage systems, molecular electronic devices,

switches and machines.2

The effect of supramolecular self-assembly of unsaturated

compounds on their photochemical properties is of particular

interest due to the possibility of controlling the route of photo-

reactions in such systems and often also their stereochemical

outcome.1a,3 For example, stereoselective PCA of stilbene

derivatives can occur in the cucurbit[8]uril and g-cyclodextrincavities and assist by crown ethers with great macrocycle size.3c,4

For stilbenes containing a crown-ether moiety, self-assembly

in the presence of metal or ammonium cations can also

be controlled rather easily via complexation. For example,

bis-sandwich complexes of bis(15-crown-5)- or bis(18-crown-

6)stilbenes [(E)-1b and (E)-1c] with K+ or Cs+ ions,

respectively, were assumed to form; their structure was not

determined.5 In the presence of metal cations with large ion

diameter (K+, Rb+, Sr2+, Ba2+), bis(15-crown-5)oligophenylene-

thylenes form stacked complexes of different structures and

stoichiometries in which stereospecific polyPCA takes place.6

The stereospecific PCA in the ammonium-containing mono-

(24-crown-8)stilbene dimeric complex was studied.7 Unusually

stable donor–acceptor complexes were found to be formed

from (E)-1c and diammonium derivatives of viologen analogues.

These complexes can serve as fluorescence molecular sensors for

alkaline-earth metal cations.8

a Photochemistry Centre, Russian Academy of Sciences,ul. Novatorov 7A-1, Moscow 119421, Russian Federation.E-mail: [email protected]; Fax: +7 495 936 1255

bN. S. Kurnakov Institute of General and Inorganic Chemistry,Russian Academy of Sciences, Leninskiy prosp. 31, Moscow 119991,Russian Federation. E-mail: [email protected];Fax: +7 495 954 1279

c A. V. Bogatskiy Physicochemical Institute,National Academy of Sciences of Ukraine,Lustdorfskaya doroga 86, Odessa 65080, Ukraine

dN. D. Zelinskiy Institute of Organic Chemistry,Russian Academy of Sciences, Leninskiy prosp. 47, Moscow 119991,Russian Federation. E-mail: [email protected]; Fax: +7 499 135 5328

e Chemistry Department,Durham University, South Road, Durham DH1 3LE, UK.E-mail: [email protected]; Fax: +44 0191 374 3745w Electronic supplementary information (ESI) available: Combinationof conformers of stilbenes (E)-1a–c within bis-sandwich complexes(Scheme S1). Disorder of stilbene molecules in the crystal (E)-1c�C3�2.67C6H6 and the structure of cyclic trimer (1c)3�(C3)3 (Fig. S1).Emission spectra of equimolar mixture of (E)-1b and Ba(ClO4)2 andits photolysates after irradiation (Fig. S2). 1H NMR spectrum of thereaction mixture after photolysis in system (E)-1b/Ba(ClO4)2 (Fig. S3).Absorption spectra of rctt-4b�(KClO4)2, rctt-4c�(CsClO4)2, and amixture of rctt-4a�[Ba(ClO4)2]2 and rtct-4a�[Ba(ClO4)2]2 (Fig. S4).CCDC reference numbers 780035–780041. For ESI and crystallo-graphic data in CIF or other electronic format see DOI: 10.1039/c0nj00780c

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This journal is c The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2011 New J. Chem., 2011, 35, 724–737 725

We found that in concentrated solutions, stilbene (E)-1c can

form hydrogen-bonded 2 : 2 bis-pseudosandwich complexes

with alkanediammonium salts H3N+(CH2)nNH3

+ 2ClO4�

(Cn, n = 2–8) (Scheme 1); for such complexes with relatively

short diammonium ions (n = 2–4), effective stereoselective

PCA proceeds to give mainly the rctt isomer of cyclobutane

derivative.9 However, photoreactions of crown-containing

stilbenes are little studied, which is due, not after all other

reasons, to the poor accessibility of these compounds.

Recently, we developed a simple and convenient synthesis of

symmetric bis(crown)stilbenes (E)-1a–c providing 70–73%

yields of these compounds from benzocrown ethers.10 We

suggested that in the presence of appropriate metal cations,

these stilbenes would form rather stable bis-sandwich 2 : 2

complexes (Scheme 2) in which the ethylene bonds of

two stilbene molecules will be proximate, and, hence, pre-

organized for PCA to give cyclobutane derivative. This article

presents our 1H NMR study of the composition and structure

of the products of photolysis of 1a–c in the presence of alkali

and alkaline-earth metal cations and compound C3. The

structures of stilbene complexes of different stoichiometries

and also the stereochemistry of the major PCA product, the

rctt isomer of 1,2,3,4-tetracrown cyclobutane, were confirmed

by X-ray diffraction study.

Results and discussion

UV/Vis and 1H NMR studies of stilbene complexes

In MeCN, free stilbenes (E)-1a–c demonstrate intense

long-wavelength absorption (LA) with lmax at B335 nm and

fluorescence with a maximum at B385 nm (e.g., Fig. 1, curves

1 and 3). Previously, we found that under these conditions,

stilbene (E)-1c fluorescence has a quantum yield of 0.30.11 The

addition of excess alkali (Li, Na, K, Rb, Cs) or alkaline-earth

(Mg, Ca, Sr, Ba) metal perchlorate to a solution of 1a–c

induced a hypsochromic shift of the LA maximum (Dlmax

up to 15 nm) and a slight decrease in its intensity, the most

pronounced changes being observed for double-charged metal

cations (e.g., Fig. 1, curve 2). This is a usual behaviour for the

formation of host–guest complexes of chromogenic crown

compounds8c,12 and this is obviously caused by the electron-

withdrawing effect of cations coordinated by the crown-ether

fragments of 1a–c.

A 1H NMR study of MeCN-d3 solutions of mixtures of

(E)-1a–c with salts of Group I and II metals demonstrated that

the spectral changes depend considerably on the size of the

crown-ether cavity of the ligand and the metal cation size. In

all cases, the signals of most methylene groups of macrocycles

1a–c underwent a downfield shift (DdH up to 0.40 ppm) upon

Scheme 1 Formation of bis-pseudosandwich complexes between

stilbene (E)-1c and alkanediammonium ions.

Scheme 2 Formation of bis-sandwich complexes between stilbenes

(E)-1a–c and large metal cations.

Fig. 1 Absorption (1, 2) and emission (3, 4) spectra of (1, 3) (E)-1b

(C = 1 � 10–5 M) and (2, 4) its equimolar mixture with Ba(ClO4)2(MeCN, 1 cm cell, ambient temperature); excitation at 270 nm.


addition of excess salt to stilbene, thus confirming binding of

the crown-ether moiety to the metal cations. Similar effects

were observed in our study of complexation of (E)-1c with

Cn.9 When the size of the macrocycle cavity was roughly the

same or larger than the metal cation diameter, the signals of

aromatic and ethylene protons of stilbene also underwent

monotonic downfield shifts following increase in the CM/C1

ratio (e.g., Fig. 2), which was caused by the electron-

withdrawing effect of the cation in the complex. Note that in

Fig. 2 the nearly linear dependence DdH � CKClO4/C1c

for CKClO4/C1c o 2 and smoothening of the curves at

CKClO4/C1c E 2 imply the formation of relatively stable

complexes 1c�K+ and 1c�(K+)2 (see below).

When the size of the macrocycle cavity was smaller than the

diameter of the metal cation, the behaviour of the signals of

aromatic and ethylene protons was, in most cases, more

complex. As an example, Fig. 3 shows the dependence

DdH � CCsClO4/C1c. It can be seen that these proton signals

of stilbene (E)-1c shift upfield (DdH up to �0.26 ppm) at

CCsClO4o C1c, and then start to vary in the opposite direction

at CCsClO4 > C1c. This means that as CsClO4 is added to a

solution of 1c, this first gives a relatively stable complex

1c�Cs+, which dimerizes spontaneously to bis-sandwich com-

plex (1c)2�(Cs+)2 owing to the possibility of binding large Cs+

ions simultaneously to two 18-crown-6-ether fragments. In this

complex, the conjugated fragments of two stilbene molecules are

stacked one above another (see Scheme 2), which results in

mutual shielding of the protons of these fragments typically

observed for other stacked supramolecular architectures we

studied previously.8,13 Further increase in the CsClO4

concentration, evidently, shifts the equilibrium toward

complex 1c�(Cs+)2, which tends to show downfield shifts of

dH with respect to the free ligand.

In the case of formation of very stable bis-sandwich

complexes [(E)-1a–c]2�(Mm+)2, pronounced broadening of

the spectral lines or even appearance of several highly over-

lapped sets of signals was observed. This is indicative of ligand

exchange between several types of complexes that is slow on

the 1H NMR time scale (500 MHz). As an example, Fig. 4a

and b presents the change of the spectrum of stilbene (E)-1b

after addition of excess Ba(ClO4)2. Analysis of the COSY

spectrum of the mixture showed that in the field of aromatic

protons, signals from at least two unsymmetrically substituted

ethylene bonds are present (3JCHQCH = 15.9–16.2 Hz), which

are marked in Fig. 4b. Since the stilbene (E)-1b structure is

symmetric, this is indicative of asymmetric structure of some

of the formed complexes (1b)2�(Ba2+)2.

Previously,10 we found that (E)-1a–c and (E)-3,4,30,40-

tetramethoxystilbene can exist in the crystals as symmetric

s-syn,s-syn and s-anti,s-anti conformers differing in the

arrangement of the ethylene bond relative to the crown-ether

moiety. In solutions, these conformers occur in fast equilibrium

in which the former predominates. This is due to the relatively

low (B5.6 kcal mol�1) energy barrier to the rotation of the

benzene ring around the formally single bond of the ethylene

fragment. It is clear that the asymmetric s-anti,s-syn conformer

Fig. 2 Values of DdH = dH(1c/KClO4 mixture) � dH(free 1c) for

some protons of (E)-1c as a function of the KClO4/1c concentration

ratio (C1c = 1 � 10–3 M, MeCN-d3, 30 1C).

Fig. 3 Values of DdH = dH(1c/CsClO4 mixture) � dH(free 1c) for

some protons of (E)-1c as a function of the CsClO4/1c concentration

ratio (C1c = 1 � 10–3 M, MeCN-d3, 30 1C).

Fig. 41H NMR spectra (the region for aromatic protons) of (a)

(E)-1b (C = 5 � 10–3 M) and (b, c) its mixture with Ba(ClO4)2(C=6� 10–3 M) in (a, b) MeCN-d3 and (c) MeCN-d3–D2O (10 : 1, v/v)

(500 MHz, 30 1C).


of stilbene should also exist in solution as an intermediate state

between the two above-mentioned symmetric conformers

(Scheme 3). The bis-sandwich complex can be formed from

two identical or different conformers of bis(crown)stilbene,

moreover, with either parallel or cross orientation of ethylene

bonds (totally 14 types of structures of bis-sandwich complexes,

A–N, shown in Scheme S1 in the ESIw to this article). To

participate simultaneously in metal cation binding, the crown-

ether moieties in such complexes should be located approximately

one above another. Since in complexes [(E)-1a–c]2�(Mm+)2, the

2-H, 3-CH2OAr, and CHQCH protons are most shielded (see

Fig. 3), some types of complexes can be suggested to pre-

dominate in solutions (see types B, D, and I in Scheme S1, ESIw).The stability constants of complexes formed by stilbenes

(E)-1a–c with metal perchlorates or diammonium compound

C3 were determined by 1H NMR titration in MeCN-d3. The

variation of DdH of the ligand protons vs. the salt-to-ligand

concentration ratio for cations whose diameter does not

exceed the macrocycle cavity size was adequately described

by the model taking into account two equilibria:

K1:1: L + Mm+ = L�Mm+ (1)

K1:2: L�Mm+ + Mm+ = L�(Mm+)2 (2)

where L is stilbene 1a–c; K1:1 is the stability constant of

complex 1a–c�Mm+, M�1; K1:2 is the stability constant of

complex 1a–c�(Mm+)2, M�1.

When the cation diameter was greater than the macrocycle

cavity, it was often necessary to take into account simultaneously

equilibria (1), (2), and (3):

K2:2: 2 L�Mm+ = (L)2�(Mm+)2 (3)

where K2:2 is the stability constant of complex (1a–c)2�(Mm+)2,

M�1. The stability constants thus found are summarized in

Table 1. Note that in some cases we failed to determine the

stability constants of L�Mm+ as they were too high and

above the upper limit of applicability of 1H NMR titration

(log K1:1 > 5) and also because of the above-noted slow ligand

exchange on the 1H NMR time scale.

It follows from the data of Table 1 that bis(18-crown-

6)stilbene (E)-1c forms all three types of complexes with

caesium and propanediammonium cations. Obviously,

only in the presence of these large cations, can rather stable

(log K2:2 Z 8.7) bis-sandwich complex (1c)2�(Cs+)2 and

bis-pseudosandwich complex (1c)2�(C3)2 be formed (see

Schemes 1 and 2). The latter complex is formed due to

complementarity of the primary ammonium group and the

18-crown-6-ether moiety and also to relatively short distance

between the two ammonium groups in C3, which probably

does not prevent stacking interactions between the two planar

stilbene fragments in some types of bis-pseudosandwich

structures.9

Bis(12-crown-4)stilbene (E)-1a forms 1 : 1 complexes of low

stability with alkali metal cations (log K1:1 r 2.6), the stability

of these complexes decreasing following increase in the cation

diameter. Therefore, only with sodium cations, was the

formation of relatively weak complexes (1a)2�(Na+)2 detected

(log K2:2 = 5.0). With double-charged barium cations, 1a

forms all three types of complexes; however, the formation of

complexes 1a�(Ba2+)2 is hampered (log K1:2 = 1.8), apparently,

due to substantial decrease in the electron-donating properties

of the macrocycle oxygen atoms, which are conjugated with

the benzene ring, in complex 1a�Ba2+. A similar trend of

decreasing the stability of 1(L) : 2(Mm+) complexes compared

to 1(L) : 1(Mm+) was also found for stilbenes 1b,c.

As was to be expected, bis(15-crown-5)stilbene (E)-1b forms

stable (log K2:2 Z 6.6) bis-sandwich complexes with large K+,

Cs+, and Ba2+ ions and, conversely, does not form such

complexes with a relatively small sodium cation or compound

C3 as the ammonium group is not complementary to the 15-

membered macroheterocycle. The slow ligand exchange in

the system 1b/Ba2+ (see above) and, evidently, very high

stability constants of 1b�Ba2+ and (1b)2�(Ba2+)2 precluded

their determination. To accelerate the exchange processes, we

gradually added deuterated water to a solution of 1b and

Scheme 3 Conformers of stilbenes (E)-1a–c.

Table 1 Stability constants of complexes of stilbenes (E)-1a–c withmetal and propanediammonium perchloratesa

Mm+(ClO4�)m, M

m+

log K1:1/log K2:2/log K1:2b

(E)-1a (E)-1b (E)-1c

Na+ 2.6/5.0/—c —d/—c/2.9 —d/—c/4.0K+ 2.0/—c/—c —d,e/> 9e/—e —d/—c/5.3Cs+ 1.8/—c/—c 1.6/6.6/—c 3.1/8.9/4.3Ca2+ 3.8/—c/2.5 —d,e/—e/—e —d,e/—c/—e

Ba2+ 4.6/7.0/1.8 —d,e/—d,e/—e —d/—c/4.7C3 2.1/—c/—c 3.1/—c/—c —d/8.7/1.9

a 1H NMR titration, MeCN-d3, 30 � 1 1C. b K1:1 = [L�M]/([L]�[M])

(M–1), K2:2 = [L2�M2]/[L�M]2 (M–1), K1:2 = [L�M2]/([L�M]�[M]) (M–1).

The total measurement errors of the stability constants were B30%.c NMR titration is inapplicable due to very low (log K o 1) value of

stability constant. d NMR titration is inapplicable due to very high

(log K>5) value of stability constant. e NMR titration is inapplicable

due to slow ligand exchange on the 1H NMR time scale.


Ba(ClO4)2 mixture. When the MeCN-d3–D2O ratio of 10 : 1

(v/v) has been attained, the 1H NMR spectrum exhibits

only one set of relatively little broadened signals (Fig. 4c);

therefore, these conditions were chosen for determination of

the stability constants of 1b complexes. The stability constants

of similar complexes of benzo-15-crown-5 ether (B15C5) were

determined under the same conditions for comparison. In this

case models taking into account the following equilibria

proved to be useful: eqn (1) and (3) for 1b and eqn (1) and

(4) for B15C5:

K2:1: L�Mm+ + L = (L)2�Mm+ (4)

where K2:1 is the stability constant of complex (B15C5)2�Mm+,

M�1. The stability constants thus found are summarized in

Table 2.

Transition to aqueous acetonitrile resulted, as expected,14 in

a considerable decrease in the stability of all types of complexes

compared to the results obtained with anhydrous MeCN-d3.

Obviously, this is caused by competitive hydration of the

cation, which weakens its ion–dipole interaction with the

crown-ether heteroatoms. In the case of highly hydrophilic

magnesium and calcium cations, the complexation in a

MeCN-d3–D2O mixture almost does not occur. The stability

of 1 : 1 complexes of B15C5 varies in the series Mg2+, Ca2+ {Sr2+ o Ba2+ o K+ E Na+, which is correlated with the

decrease in the hydrophilicity of these cations. It is known that

B15C5 and its derivatives are also able to form sandwich

complexes (L)2�Mm+ with large potassium, strontium, and

barium cations;13a,f however, the stability of complexes

(B15C5)2�Mm+ in aqueous MeCN-d3 proved even lower than

that for B15C5�Mm+. In the presence of K+, Sr2+, and Ba2+

ions, the stilbene derivative can form rather stable complexes

1b�Mm+ (log K1:1 Z 3.0), which are largely dimerized

(log K2:2 Z 4.8). The much higher stability of 1 : 1 and

2 : 2 complexes formed by 1b and large metal cations

compared to 1 : 1 and 2 : 1 complexes formed by B15C5

may be related to (i) benefit of the stacking interactions in

bis-sandwich complexes and (ii) cumulative effect caused by

the presence of two crown-ether fragments in stilbene.

Complexes of stilbenes (E)-1a–c with metal picrates and

perchlorates and with compound C3 were obtained as solids

by slow saturation of acetonitrile solutions of a components

mixture by benzene or benzene–dioxane vapour; their

formal stoichiometry, 1(L) : 1(Mm+) or 1(L) : 2(Mm+), was

confirmed by elemental analysis data (see Experimental section).

Note that bis(18-crown-6)stilbene 1c forms crystalline

precipitates of 1(L) : 2(Mm+) composition with salts of metal

cations having small size as compared with the macrocycle

cavity even when the salts are present in equimolar amount in

the solution. In the case of stilbene 1b and salts of metal

cations having small size with respect to the 15-membered

macrocycle, both 1(L) : 1(Mm+) and 1(L) : 2(Mm+) crystalline

complexes can be obtained.

X-Ray diffraction studies of complexes of stilbenes (E)-1b,c

Some stilbene complexes were prepared as single crystals,

which were studied by X-ray diffractometry. Fig. 5 shows

the main components of crystals 1b�2NaClO4, 1b�2Ca(ClO4)2�2MeCN�4H2O, 1b�KPic�C6H6, 1c�CsPic�C6H6, and 1c�C3�2.67C6H6 (Pic is the picrate anion). It should be noted that

the structure 1b�2NaClO4 was determined with high errors due to

a bad quality of crystals. However, we included it in the article to

show a diversity of the coordination mode of stilbene to a metal

cation and do not discuss thin details of its geometry.

The first two structures are 1(L) : 2(Mm+) complexes. Each

metal cation is coordinated by only one crown-ether fragment;

the rest coordination sites are occupied by perchlorate anions

or solvent molecules. In spite of somewhat similarity of these

structures, they have pronounced distinctions. In 1b�2NaClO4,

the metal cations are attached at bis(15-crown-5)stilbene on

the same side of its mean plane, whereas, in 1b�2Ca(ClO4)2�2MeCN�4H2O, the metal cations are attached at the ligand

on the opposite sides.

In crystal, complex 1b�2Ca(ClO4)2 occupies a special

position in the symmetry centre that coincides with the

midpoint of the ethylene bond. As a result, the chromophore

fragment of stilbene molecule is perfectly planar. In crystal

1b�2NaClO4, the stilbene molecule occupies a general position.

However, its chromophore fragment is only slightly twisted,

the dihedral angle between the benzene rings being 6.41. This

fact together with the planarity of C–O–C(Ar)–C(Ar) fragments

(the torsion angles are close to 0 or 1801) attest to a relatively

high degree of the conjugation over the whole chromophore.

Nevertheless, the ethylene bonds in both complexes are essentially

localized, which is typical of stilbene derivatives. For both

metallocomplexes 1b�(Mm+)2, the s-syn,s-syn conformation of

stilbene molecule is found, whereas the s-anti,s-anti conformation

was revealed for the crystalline free (E)-1b.10

The sodium and calcium cations are coordinated by

all heteroatoms of the 15-membered macrocycles. Their

displacements from the mean plane through the heteroatoms

of the nearest macrocycle is only 0.60, 0.68 A for two

independent Na(1), Na(2) ions and 1.14 A for the Ca(1) ion,

i.e., the metal cations are rather deeply immersed into the

macroheterocycle cavities of stilbene 1b. This is well correlated

with published data on the compliance of the Na+ and Ca2+

ion diameters with the 15-crown-5-ether cavity.15

The coordination sphere of each of Na(1), Na(2) ions also

comprises two oxygen atoms of perchlorate anions. In the case

Table 2 Stability constants of complexes of stilbene (E)-1b andbenzo-15-crown-5 ether (B15C5) with metal and propanediammoniumperchloratesa

Mm+(ClO4�)m, M

m+(E)-1b B15C5log K1:1/log K2:2

b log K1:1/log K2:1b

Na+ 1.9/—c 2.9/—c

K+ 3.0/7.4 2.8/2.4Mg2+ —c/—c —c/—c

Ca2+ —c/—c —c/—c

Sr2+ 3.2/4.8 1.8/1.7Ba2+ 3.9/6.1 2.5/2.2C3 1.3/—c 1.4/—c

a 1H NMR titration, MeCN-d3–D2O (10 : 1, v/v), 30 � 1 1C.b K1:1 = [L�M]/([L]�[M]) (M–1), K2:2 = [L2�M2]/[L�M]2 (M–1),

K2:1 = [L2�M]/([L�M]�[L]) (M–1). The total measurement errors of

the stability constants were B30%. c NMR titration is inapplicable

due to very low value of stability constant (log K o 1).


of the complex with Ca2+ ions, the cation coordination sphere is

completed by two water and one MeCN molecules. This type of

the coordination is also encountered in the complexes of calcium

cations with benzo-15-crown-5-ether derivatives in crystal.16

Our attempts to grow single crystals of 2(L) : 2(Mm+)

complexes of stilbenes (E)-1a–c with K, Cs, Sr, Ba perchlorates

suitable for X-ray diffraction failed; the crystals formed were

of too high mosaicity. This obstacle has been overcome by

replacing the relatively small ClO4� anion for the more bulky

picrate anion. Complexes 1b�KPic and 1c�CsPic are examples

of bis-sandwich structures (types F and K, respectively, in

Scheme S1, ESIw), in which stilbene molecule 1b is represented

by s-anti,s-syn conformer and two independent molecules 1c

are shown as s-anti,s-syn and s-syn,s-syn conformers.

In both bis-sandwich complexes, the chromophore fragments

are nearly planar: the dihedral angles between the benzene ring

planes are 14.51 in 1b�KPic and 11.9, 9.01 in 1c�CsPic. As in the

previous structures, the ethylene bonds in both complexes are

essentially localized.

In 1b�KPic, the bis-sandwich complex is located in a

symmetry centre; therefore, the ethylene bonds and the

mean planes of the stilbene chromophore fragments are

strictly parallel. The intermolecular C� � �C distances between

the adjacent ethylene fragments, C(15)� � �C(16A) and

C(16)� � �C(15A), are equal to 4.56 A. With this geometry, the

overlapping of these fragments of the conjugated system is

actually lacking. In 1c�CsPic, the bis-sandwich complex is

nonsymmetric; it occupies a general position in the crystal

unit cell. The mean planes of the chromophores of two

independent stilbene molecules are inclined to each other by

angle 2.51 and the ethylene bonds of these fragments are

somewhat twisted by B211; the C(17)� � �C(51) and

C(18)� � �C(52) distances between their carbon atoms are 4.03

and 3.93 A.

The potassium and caesium cations are sandwiched by two

macroheterocycles and coordinated by all of their heter-

oatoms. Displacements of these cations from the mean plane

through all heteroatoms of the neighbouring macrocycle are

1.67, 1.66 A for the K(1) ion and 1.67–1.75 A for the Cs(1),

Cs(2) ions, i.e. these large metal cations are positioned

approximately above the centres of the macroheterocycle

cavities of stilbenes 1b,c. These parameters are close to analogous

characteristics for structurally investigated sandwich complexes

between benzo-15-crown-5-ether derivatives and K+ ions17

and between benzo-18-crown-6-ether derivative and Cs+

ions.18

In crystal 1c�C3�2.67C6H6, the stilbene molecule is present

as its s-anti,s-syn conformer. This molecule is disordered over

two close positions related by 2-fold axis with equal occupancies.

The chromophore fragment is approximately planar—the

dihedral angle between the planes of the benzene rings is

12.31. The 18-crown-6-ether moieties of 1c coordinate to the

NH3+ groups from two dications of compound C3, forming

normal or bifurcate hydrogen bonds N+–H� � �O(macrocycle).

However, instead of expected bis-pseudosandwich structure

(1c)2�(C3)2, the components in the crystal form an unusual

chiral trimer (1c)3�(C3)3 of the cyclic structure in accordance

with the R32 space group (see Fig. S1, ESIw). In this trimer,

there are no stacking interactions of the stilbene conjugated

systems and, consequently, the PCA reaction is impossible

in the solid state. Obviously, in solution such exotic

trimer structures can transform to give bis-pseudosandwich

complexes, in which the PCA reaction occurs (see below).

Fig. 5 Structure of the main components of the crystals (a) (E)-1b�2NaClO4, (b) (E)-1b�2Ca(ClO4)2�2MeCN�4H2O, (c) (E)-1b�KPic�C6H6, (d) (E)-1c�CsPic�C6H6, and (e) (E)-1c�C3�2.67C6H6. Thermal

ellipsoids are drawn at the (a, b) 50, (c, e) 40, or (d) 30% probability

level. The additional letters ‘‘A’’ and ‘‘B’’ indicate that atoms belong to

symmetrically related positions. Coordination bonds and hydrogen

bonds are drawn with dash lines.


Photochemical study of stilbenes (E)-1a–c and their complexes

The irradiation of MeCN solutions of equimolar mixtures of

1a–c with salts that form relatively stable 2(L) : 2(Mm+)

stilbene complexes induced fast changes in the absorption

spectra of photolysates, resulting in disappearance of the LA

above 300 nm (e.g., Fig. 6). The fluorescence quenching

observed during the formation of these complexes (see

Fig. 1, curves 2 and 4) continues also during irradiation and

results in almost complete disappearance of the emission (e.g.,

Fig. S2, ESIw). These facts are indicative of the substantial

violation of conjugation in the stilbene chromophores as a

result of photochemical reactions.

A 1H NMR study has shown that UV irradiation of

solutions of free (E)-1a–c in MeCN for 2 h gives rise to a

mixture of six compounds (Scheme 4, Table 3) with Z isomer

of stilbene predominating (cf. ref. 5 and 9). The photolysates

were also found to exhibit signals for phenanthrene derivatives,

namely, symmetric sym-2a–c and asymmetric asym-2a–c,

which are usual products of electrocyclic reactions of (Z)-

stilbenes followed by oxidation of the intermediate dihydro-

phenanthrenes with air oxygen.1c The characteristic signals of

aromatic protons of compounds 2 appear at d 7.4–9.2, which is

typical of annelated aromatic compounds. The minor products

include those formed upon extensive photooxidation, namely,

40-formylbenzocrown ethers 3a–c (compound 3c was also

detected previously upon long-term photolysis of 1c in CH2Cl2in the presence of iodine and air oxygen)5 and centrosymmetric

derivatives of cyclobutane rctt-4b,c. The latter compounds are

obviously formed from dimeric pairs [(E)-1b,c]2, which can be

formed owing to the intermolecular stacking interactions

of conjugated stilbene fragments. The low yield of rctt-4b,c

(o2 mol%) points to low content of dimeric pairs [(E)-1b,c]2in solution under these conditions.

Under comparable conditions, experiments on irradiation

of solutions (E)-1a–c in the presence of Group I and II metal

perchlorates and diammonium compound C3 were carried

out. Data on the compositions and the ratio of photolysis

products are summarized in Table 3.

It was found that the presence of cations that are complexed

with stilbenes 1a–c (log K1:1 > 5) to form relatively stable

complexes 1�Mm+, which do not tend to dimerize to bis-sandwich

structures, resulted only in suppression of oxidative processes

and, as a consequence, in increase in the content of (Z)-1 in the

photolysate. Apparently, the complexation with the cation

prevents both intramolecular electrocyclic reactions of stilbene

and its participation in the intermolecular [2+2] photo-

cycloaddition due to the Coulomb repulsion of the positively

charged complexes in the dimeric pair [(E)-1]2�(Mm+)2, which

should precede the formation of 4.

Conversely, in the presence of metal cations complexed with

stilbenes to give fairly stable complexes such as (E)-1�Mm+

and [(E)-1]2�(Mm+)2 (log K1:1 Z 4.6, log K2:2 Z 7.0),

cyclobutane derivatives rctt-4a–c were the major photo-

products formed in the reaction (64–85 mol%) as a result of

PCA in bis-sandwich complexes with the conjugated fragments

being located approximately one above another and the

ethylene bonds being parallel. Note that in these systems, the

formation of oxidation products 2 and 3 sharply decreases

often down to their total absence in the reaction mixture. This

attests indirectly to the relatively high content of bis-sandwich

complexes and high efficiency of PCA in them. This is probably

possible owing to rather close arrangement of the ethylene

bonds in these complexes favourable for cycloaddition, i.e.,

their pre-organization for PCA. Apart from (Z)-1a–c and

Fig. 6 Absorption spectra of (1) equimolar mixture of (E)-1b and

Ba(ClO4)2 (C = 1 � 10–5 M, MeCN, 1 cm cell, ambient temperature)

and its photolysates after irradiation over (2) 0.8, (3) 2, (4) 3, (5) 5, and

(6) 25 s.

Scheme 4 Photolysis products of stilbenes 1a–c.


major rctt-4a–c, minor rtct cyclobutanes 4a–c (3–27 mol%)

were also detected; obviously, these are formed upon PCA of

complexes [(E)-1a–c]2�(Mm+)2 with crossed ethylene bonds

(for example, see structure of type B in Scheme S1, ESIw).Note unusual photochemical properties of systems

1b/Ca2+(Mg2+). In view of the similarity of the cavity size

of the 15-membered macrocycle and the metal cation

diameters, one could expect the absence of formation of

stable 2(L) : 2(M2+) complexes and, hence, low content of

cyclobutanes 4b in the photolysis products. Conversely, it was

found that cycloaddition of 1b in the presence of Ca2+ ions is

only slightly slower than that in the 1b/Ba2+(Sr2+) systems,

moreover, the selectivity of formation of rctt-4b/rtct-4b is even

higher. A similar situation was observed for Mg2+ ions but the

rate of PCA was considerably lower. Presumably, this unusual

behaviour is due to partial hydration of the relatively small

alkaline-earth metal cation complexed with the benzo-15-

crown-5-ether fragment. As shown by X-ray diffraction study

of 1b�2Ca(ClO4)2, the calcium coordination sphere may

additionally contain three rather small solvation molecules,

for example, water molecules (see Fig. 5b). The hydrogen

atoms of these water molecules are directed away from the

stilbene 1b basis molecule, thus creating the binding site for a

second stilbene molecule through hydrogen bonding to the

oxygen atoms of its free macrocyclic fragment (Scheme 5).

Apparently, the complexation in solution involves hydrated

ions, [Ca(H2O)x]2+ or [Mg(H2O)x]

2+ (x = 1–3), whose

effective diameter may be even greater than the diameter of

the largest studied barium and caesium cations. The high

stereoselectivity of PCA in the systems 1b/Ca2+(Mg2+) is

attributable to more stringent requirements to the orientation

of stilbene molecules in complexes [(E)-1b]2�{[M(H2O)x]2+}2,

imposed by hydrogen bonding.

The signals of aromatic and cyclobutane protons of cyclo-

butane isomers, rctt-4a–c and rtct-4a–c, are substantially

different (for example, Fig. S3, ESIw). This provides reliable

identification of the isomers. In a DMSO-d6 solution, all

aromatic signals of the rtct isomer are shifted downfield

(DdH up to 0.26 ppm) with respect to analogous signals of

the rctt isomer, and, conversely, the cyclobutane proton signal

for rtct-4 (singlet at d E 3.4) is located at higher field than the

analogous signal of rctt-4 (singlet at dE 4.3).9 This is a typical

spectral behaviour for the corresponding isomers of the

1,2,3,4-tetraaryl-containing cyclobutane19 caused by the trans

arrangement relative to each other of all vicinal substituents in

the cyclobutane ring of rtct-4a–c and mixed, trans and cis

arrangement in the case of rctt-4a–c.

The major photoproducts in the systems 1b/KClO4,

1b/Ca(ClO4)2, 1c/CsClO4, and 1c/C3 were isolated by crystall-

ization as complexes rctt-4b�(KClO4)2, rctt-4b�[Ca(ClO4)2]2,

rctt-4c�(CsClO4)2, and rctt-4c�(C3)2, respectively. Their structureswere confirmed by 1H and 13C NMR spectroscopy and

elemental analysis data. The absorption spectra of these

complexes are characterized by disappearing of the absorption

at >300 nm (for example, see Fig. S4, ESI1); this confirms the

violation of the chromophore conjugation chain in cyclobutane.

Free cyclobutanes rctt-4b and rctt-4c were prepared by

decomplexation of rctt-4b�[Ca(ClO4)2]2 by ethylenediaminetetra-

acetic acid in the presence of Me4NOH and by decomplexation

of rctt-4c�(C3)2 or rctt-4c�(C4)29 in a water–organic solvent

mixture (see Experimental section).

X-Ray diffraction studies of metal complexes of cyclobutane

rctt-4b

The structures of two metal complexes of rctt-4b were

determined by X-ray diffraction. Fig. 7 shows the structure of

the key components of the crystal unit cells of these complexes.

In crystal rctt-4b�2KClO4, the cyclobutane molecule

occupies a special position on crystallographic axis 2, which

passes through the midpoints of the bonds of the cyclobutane

ring, C(1)–C(1A) and C(16)–C(16A). The cyclobutane ring

exists in a non-planar conformation: the torsion angles at the

C(1)–C(16)–C(16A)–C(1A) ring range from �14.9 to 14.61.

The dihedral angle between the planes of the cis-arranged

benzene rings is only 23.21; these rings are proximate in space

in such a way that the crown-ether fragments connected to

Table 3 Composition and the ratio of the photolysis products ofstilbene 1a–c solutions in the absence and presence of metal andpropanediammonium perchloratesa

Stilbene Salt, Mm+

Photolysate composition (mol%)b

(E)-1 (Z)-1 sym-2 asym-2 3 rctt-4 rtct-4

1a —c 8.6 73.1 11.0 6.3 1.0 0 0Li+ 10.2 67.5 10.5 8.9 2.9 0 0Na+ 8.5 62.1 12.9 8.6 0.7 7.2 0K+ 11.4 58.0 12.7 13.4 4.5 0 0Cs+ 10.1 61.3 13.2 11.7 3.7 0 0Mg2+ 11.7 61.7 13.7 8.6 4.3 0 0Ca2+ 10.2 84.6 4.1 1.0 0.1 0 0Sr2+ 1.8 6.9 1.9 0.7 2.1 64.0 22.6Ba2+ 0 0 0 0 7.5 65.5 27.0

1b —c 12.8 55.6 17.8 7.8 4.4 1.6 0Li+ 12.5 65.3 11.1 7.7 3.4 0 0Na+ 12.3 68.5 9.6 6.9 2.7 0 0K+ 0 0 0 0 0 84.0 16.0Rb+ 3.1 0 3.5 2.3 2.0 82.9 6.2Cs+ 7.2 35.7 18.9 9.3 6.4 19.5 3.0Mg2+ 8.0 55.7 5.1 0 0 28.4 2.8Ca2+ 0 20.0 0 0 0 76.9 3.1Sr2+ 0 0 0 0 0 85.5 14.5Ba2+ 0 0 0 0 0 74.1 25.9C3 6.2 77.2 5.4 0 6.2 5.0 0

1c —c,d 12.4 55.0 17.5 8.1 5.1 1.9 0K+ 13.6 67.0 8.7 7.3 3.4 0 0Rb+ 12.8 62.9 13.5 6.6 4.2 0 0Cs+ 1.1 3.3 3.7 0.7 1.5 73.5 16.2Ba2+ 12.1 73.8 5.3 3.5 2.4 2.9 0C3d 0 12.6 0 0 0.1 83.8 3.5

a MeCN, C1 = 1 � 10�3 M, 1.1 equiv. Mm+(ClO4�)m or

H3N+(CH2)3NH3

+ 2ClO4� (C3). b According to the 1H NMR

spectral data. c Without salt. d Data from ref. 9.

Scheme 5 Possible structure of complex [(E)-1b]2�{[Ca(H2O)3]2+}2.


them coordinate the K(1) cation, thus forming an intramolecular

sandwich complex. The potassium cation is located almost

exactly in the middle between two 15-membered macrocycles

and is coordinated by all of their oxygen atoms: the displacements

of the cation from the mean planes through all heteroatoms of

the two macrocycles are 1.72 and 1.68 A. These parameters are

similar to analogous characteristics of bis-sandwich structure

1b�KPic�C6H6 (see above); apparently, the PCA reaction does

not induce considerable steric strain on passing from the initial

complex [(E)-1b]2�(K+)2 to rctt-4b�(K+)2.

In crystal rctt-4b�2Ca(ClO4)2, the cyclobutane molecule

occupies a general position. The cyclobutane ring is non-

planar: the torsion angles at the C(1)–C(2)–C(3)–C(4) ring

vary from �21.6 to 21.21. The dihedral angles between the

planes of cis-arranged benzene rings are 47.6 and 35.61. These

rings are more remote from each other than in the previous

structure; therefore, only two crown-ether fragments coordinate

relatively small Ca(1) and Ca(2) cations, whereas the other two

macrocycles do not participate in their binding. The deviations

of cations from the mean plane through all heteroatoms of the

nearest macrocycle are 1.15 and 1.11 A. These parameters are

similar to those characteristics of the crystalline complex

1b�2Ca(ClO4)2 (see above). As in the mentioned complex, in

this case, the coordination sphere of each independent

calcium cation contains three water molecules. Typically, the

O(1W),. . .,O(6W) water molecules connected to calcium

cations are located in space between the two cis-arranged

benzo-15-crown-5-ether fragments. Although the hydrogen

atoms of these water molecules were not localized, the shortest

O(water)� � �O(free macrocycle) distances are in the range of

2.72–2.79 A, which implies the presence of a hydrogen

bond network between the indicated water molecules and the

oxygen atoms of free macrocycles. Thus, the found structural

characteristics of rctt-4b�2Ca(ClO4)2 indirectly confirm that

bis-sandwich complex [(E)-1b]2�{[Ca(H2O)3]2+}2 (see Scheme 5)

may exist in solution, which should precede the formation of

the cyclobutane derivative.

Note that the structure of cyclobutane rctt-4c as the

complex with diammonium compound C4 was determined in

our recent X-ray diffraction study.9 The formation of this

compound could have been preceded by bis-pseudosandwich

complex [(E)-1c]2�(C4)2, consisting of stilbene s-syn,s-syn and

s-anti,s-anti conformers (structure of type I in Scheme S1,

ESIw). From the consideration of the crystal structures of

rctt-4b�2KClO4 and rctt-4b�2Ca(ClO4)2 it follows that the

cyclobutane rctt-4b might be formed from the bis-sandwich

complexes of the same type. Thus, although free stilbenes

(E)-1a–c are highly conformationally flexible and can be

assembled in the presence of metal cations or diammonium

compounds to bis-(pseudo)sandwich structures with various

mutual orientation of chromophores and ethylene bonds, the

indirect evidence that the [2+2] photocycloaddition occurs

only for one type of complexes to give the rctt isomers has

been obtained.

Conclusions

Thus, we studied systematically the characteristic features of

complexation of symmetric bis(crown)stilbenes with Group I,

II metal cations and H3N+(CH2)3NH3

+ ions and for the first

time elucidated their influence on the photoreaction route.

Three types of stilbene self-assembly were studied: (i) by means

of metal cations, (ii) by means of hydrogen bonds, and

(iii) mixed type self-assembly. Large metal cations whose

diameter exceeds the size of stilbene macrocycle cavity promote

the formation of stable unusual bis-sandwich 2(L) : 2(Mm+)

complexes, in which two stilbene molecules are located one

above another and their ethylene bonds are close in space.

Complexes of similar structure are formed by bis(15-crown-5)-

stilbene in the presence of hydrated ions, [Ca(H2O)x],2+

[Mg(H2O)x]2+, and by bis(18-crown-6)stilbene with propane-

diammonium ions. In these complexes, two stilbene molecules

are held together through numerous hydrogen bonds. In

bis-(pseudo)sandwich complexes, stereoselective [2+2] photo-

cycloaddition takes place to give mainly rctt isomers of

tetracrown cyclobutanes, which were studied by X-ray diffraction.

The identified trends allow one to control the direction of

phototransformation of bis(crown)stilbenes, which can be

used to obtain new homotetratopic receptors and for optical

data recording systems.

Experimental section

General

The melting points were measured with a Mel-Temp II

apparatus in a capillary and are uncorrected. The 1H and13C NMR spectra were recorded on a Bruker DRX500

instrument in DMSO-d6 and MeCN-d3 at 25–30 1 using the

solvent as the internal reference (dH 2.50 and 1.96, respectively;

dC 39.43 for DMSO-d6); J values are given in Hz. 1H–1H

COSY and ROESY spectra and 1H–13C COSY (HSQC and

Fig. 7 Structure of the main components of crystals (a) rctt-4b�2KClO4�2C6H6�4H2O and (b) rctt-4b�2Ca(ClO4)2�3C6H6�9H2O. Thermal

ellipsoids are drawn at the 50% probability level. The additional letter

‘‘A’’ indicates that atoms belong to symmetrically related positions.

Coordination bonds are drawn with dash lines.


HMBC) spectra were used to assign the proton and carbon

signals (see Schemes 2 and 4 for atom numbering). Absorption

and emission spectra were recorded on a UV-3101PC spectro-

photometer and a RF-5301PC spectrofluorimeter (Shimadzu)

in the range of 200–500 and 280–600 nm, respectively, with an

increment of 1 nm in MeCN (spectroscopic grade, the

water content r0.03%, Cryochrom, Russian Federation) at

ambient temperature using 1-cm quartz cells. High resolution

ESI mass spectra were measured on a MicrOTOF II

instrument (Bruker Daltonics) in the range of

m/z = 50–3000 for positive ions (MeCN solution inlet,

nitrogen gas flow, 4500 V capillary voltage). Elemental

analyses were performed at the microanalytical laboratory

of the A. N. Nesmeyanov Institute of Organoelement

Compounds (Moscow, Russian Federation).

Preparations

Ethylenediaminetetraacetic acid, Me4NOH (20%, aq.), and

water (HPLC grade) were used as received (Aldrich). All metal

perchlorates (Aldrich) were dried at 200 1C in vacuo. K, Cs,

and Ba picrates were obtained by neutralization of aqueous

KOH, CsOH, and BaO with a 5% excess of picric acid

(Aldrich) followed by evaporation to dryness in vacuo, washing

with abs. EtOH, and drying in air. Stilbenes (E)-1a–c,10 benzo-

15-crown-5 ether,20 and salt H3N+(CH2)3NH3

+ 2ClO4�

(C3)13d were obtained according to known procedures.

Complexes between stilbenes (E)-1a–c and salts (general

method)

A solution of a mixture of stilbene (E)-1a–c and metal

perchlorate or picrate (1 or 2 equiv.) or compound C3

(1 equiv.) in MeCN (3–5 cm3) was slowly saturated with

benzene or benzene–dioxane mixture (B2 : 1, v/v) by the

vapour diffusion method at ambient temperature in the dark

until a precipitate was formed (for 1–2 weeks). The precipitate

was separated by decantation and dried at 80 1C in vacuo.

Complex [(E)-1a]2�[Ba(ClO4)2]2 was obtained from

(E)-1a (9.5 mg, 20.1 mmol) and Ba(ClO4)2 (6.6 mg, 19.6 mmol)

as a white powder (14.4 mg, 87%); mp>360 1C (dec.) (Found:

C, 39.50; H, 4.03. Calc. for 2C26H32O8�2BaCl2O8�2MeCN:

C, 39.57; H, 4.15%).

Complex (E)-1b�NaClO4 was obtained from (E)-1b

(20.6 mg, 36.8 mmol) and NaClO4 (4.5 mg, 36.6 mmol) as

small colourless crystals (20.1 mg, 80%); mp >310 1C (dec.)

(Found: C, 52.81; H, 5.92. Calc. for C30H40O10�NaClO4: C,

52.75; H, 5.90%).

Complex [(E)-1b]2�(KClO4)2 was obtained from (E)-1b

(9.8 mg, 17.5 mmol) and KClO4 (2.5 mg, 18.0 mmol) as small

colourless crystals (10.9 mg, 89%); mp >340 1C (dec.)

(Found: C, 51.41; H, 5.71. Calc. for 2C30H40O10�2KClO4: C,

51.53; H, 5.77%).

Complex [(E)-1b]2�(KPic)2 was obtained from (E)-1b (8.7

mg, 15.5 mmol) and potassium picrate (4.1 mg, 15.4 mmol) as

yellow crystals (11.8 mg, 87%); mp 249–251 1C (Found: C,

53.04; H, 5.40; N, 4.61. Calc. for 2C30H40O10�2C6H2KN3O7�0.5C6H6�H2O: C, 52.59; H, 5.24; N, 4.91%).

Complex [(E)-1b]2�(CsClO4)2 was obtained from (E)-1b

(17.8 mg, 31.8 mmol) and CsClO4 (7.4 mg, 31.8 mmol) as small

colourless crystals (22.3 mg, 88%); mp 274–278 1C (dec.)

(Found: C, 45.36; H, 4.98. Calc. for 2C30H40O10�2CsClO4:

C, 45.44; H, 5.08%).

Complex (E)-1b�Mg(ClO4)2 was obtained from (E)-1b

(20.3 mg, 36.3 mmol) and Mg(ClO4)2 (8.0 mg, 35.7 mmol) as


(Found: C, 45.94; H, 5.19. Calc. for C30H40O10�MgCl2O8: C,

45.97; H, 5.14%).

Complex (E)-1b�[Mg(ClO4)2]2 was obtained from (E)-1b

(9.9 mg, 17.7 mmol) and Mg(ClO4)2 (8.4 mg, 37.5 mmol) as


(Found: C, 35.60; H, 4.19. Calc. for C30H40O10�2MgCl2O8: C,

35.78; H, 4.00%).

Complex (E)-1b�[Ca(ClO4)2]2 was obtained from (E)-1b

(11.6 mg, 20.7 mmol) and Ca(ClO4)2 (5.0 mg, 20.9 mmol) as


(Found: C, 37.84; H, 4.31. Calc. for C30H40O10�2CaCl2O8�C6H6�2H2O: C, 37.51; H, 4.37%).

Complex [(E)-1b]2�[Sr(ClO4)2]2 was obtained from

(E)-1b (12.9 mg, 23.0 mmol) and Sr(ClO4)2 (6.6 mg, 23.0 mmol)

as small colourless crystals (17.2 mg, 88%); mp>340 1C (dec.)

(Found: C, 42.37; H, 4.71. Calc. for 2C30H40O10�2SrCl2O8: C,

42.53; H, 4.76%).

Complex [(E)-1b]2�[Ba(ClO4)2]2 was obtained from

(E)-1b (12.8 mg, 22.9 mmol) and Ba(ClO4)2 (7.8 mg, 23.2 mmol)

as small colourless crystals (18.9 mg, 92%); mp>340 1C (dec.)

(Found: C, 39.96; H, 4.38. Calc. for 2C30H40O10�2BaCl2O8: C,

40.18; H, 4.50%).

Complex (E)-1c�(KClO4)2 was obtained from (E)-1c

(20.3 mg, 31.3 mmol) and KClO4 (4.3 mg, 30.9 mmol) as small


(Found: C, 44.41; H, 5.10. Calc. for C34H48O12�2KClO4: C,

44.11; H, 5.23%).

Complex [(E)-1c]2�(CsClO4)2 was obtained from (E)-1c

(10.9 mg, 16.8 mmol) and CsClO4 (4.0 mg, 17.2 mmol) as

colourless crystals (12.6 mg, 85%); mp 260–263 1C (dec.)

(Found: C, 46.44; H, 5.48. Calc. for 2C34H48O12�2CsClO4:

C, 46.35; H, 5.49%).

Complex [(E)-1c]2�(CsPic)2 was obtained from (E)-1c

(15.2 mg, 23.5 mmol) and caesium picrate (8.4 mg, 23.3 mmol)

as small yellow druses (22.1 mg, 91%); mp 210–213 1C

(Found: C, 49.74; H, 5.16; N, 3.77. Calc. for 2C34H48O12�2C6H2CsN3O7�1.5C6H6: C, 50.03; H, 5.14; N, 3.93%).

Complex (E)-1c�[Ba(ClO4)2]2 was obtained from (E)-1c

(6.9 mg, 10.7 mmol) and Ba(ClO4)2 (3.6 mg, 10.7 mmol) as a

white powder (6.1 mg, 77%); mp >365 1C (dec.) (Found: C,

33.90; H, 4.05. Calc. for C34H48O12�2BaCl2O8�4MeCN: C,

33.96; H, 4.07%).

Complex (E)-1c�[Ba(Pic)2]2 was obtained from (E)-1c

(2.7 mg, 4.2 mmol) and barium picrate (4.7 mg, 7.9 mmol) as

an orange powder (4.7 mg, 62%); mp 207–209 1C (Found: C,

37.94; H, 3.06; N, 8.40. Calc. for C34H48O12�2C12H4BaN6O14�0.5C6H6�3H2O: C, 37.98; H, 3.40; N, 8.71%).

Complex [(E)-1c]3�(C3)3 was obtained from (E)-1c

(12.2 mg, 18.8 mmol) and compound C3 (5.1 mg, 18.6 mmol)

as colourless crystals (16.4 mg, 92%); mp >260 1C

(dec.) (Found: C, 49.85; H, 6.71; N, 2.77. Calc. for

3C34H48O12�3C3H12Cl2N2O8�1.5C6H6: C, 49.90; H, 6.60; N,

2.91%).


Photolysis of stilbenes (E)-1a–c and their complexes with metal

perchlorates and salt C3 (general procedure)

A solution of a mixture of (E)-1a–c (15.4 mmol) and

Mm+(ClO4�)m or C3 (16.9 mmol) (or without salt) in MeCN

(15 cm3, spectroscopic grade) was placed in a quartz cell

(5 cm � 4.5 cm � 1 cm), and the mixture was irradiated for

2 h with stirring with the light from a L8253 xenon lamp

(Hamamatsu, maximum power, A9616-05 light filter

(transmission 320–420 nm), distance to the light source

10 cm) from the side of the largest facet of the cell. The solvent

was thoroughly evaporated in vacuo and the solid residue was

analyzed by 1H NMR spectroscopy (in DMSO-d6), comparing

the integral intensities of signals. The data on the product

composition are given in Table 3.

12,12 0,1200,12 0 0 0-Cyclobutane-r-1,c-2,t-3,t-4-tetrayltetrakis-

2,3,5,6,8,9-hexahydro-1,4,7,10-benzotetraoxacyclododecine rctt-4a

and 12,120,1200,120 0 0-cyclobutane-r-1,t-2,c-3,t-4-tetrayltetrakis-

2,3,5,6,8,9-hexahydro-1,4,7,10-benzotetraoxacyclododecine rtct-4a,

complexes with Ba(ClO4)2. A solution of a mixture of (E)-1a

(7.2 mg, 15.3 mmol) and Ba(ClO4)2 (5.6 mg, 16.8 mmol) in

MeCN (15 cm3) was irradiated for 2 h according to the above

described procedure. According to 1H NMR data, the reaction

mixture consisted of rctt-4a, rtct-4a, and 40-formylbenzo-12-

crown-4 ether (3a) in 8.7 : 3.6 : 1 molar ratio; lmax(MeCN)/

nm 282 (e/dm3 mol�1 cm�1 11 800); m/z (ESI MS) 495.1935

(calc. for C52H64O16�2Na+: 495.1995) and 967.4023 (calc. for

C52H64O16�Na+: 967.4092). rctt-4a: dH(500 MHz; DMSO-d6;

30 1C) 3.54 (16 H, s, 8 � CH2O), 3.55 (8 H, m, 4 �CH2CH2OAr), 3.60 (8 H, m, 4 � CH2CH2OAr), 3.90 (8 H,

m, 4 � CH2OAr), 3.98 (8 H, m, 4 � CH2OAr), 4.27 (4 H, s, 4

� CHAr), 6.75 (4 H, d, J 1.8, 4 � 2-H), 6.76 (4 H, dd, J 8.2

and 1.8, 4 � 6-H) and 6.82 (4 H, d, J 8.2, 4 � 5-H). rtct-4a:

dH(500 MHz; DMSO-d6; 30 1C) 3.40 (4 H, s, 4 � CHAr), 3.61

(16 H, s, 8 � CH2O), 3.68 (16 H, m, 8 � CH2CH2OAr), 4.04

(8 H, m, 4 � CH2OAr), 4.07 (8 H, m, 4 � CH2OAr), 6.91 (4 H,

dd, J 8.2 and 1.8, 4 � 6-H), 6.94 (4 H, d, J 8.2, 4 � 5-H) and

7.01 (4 H, d, J 1.8, 4 � 2-H).


2,3,5,6,8,9,11,12-octahydro-1,4,7,10,13-benzopentaoxacyclopenta-

decine rctt-4b, complex with KClO4. A solution of a mixture of

(E)-1b (29.4 mg, 52.5 mmol) and KClO4 (7.3 mg, 52.5 mmol) in

MeCN (15 cm3) was irradiated for 10 h according to the above

described procedure. The reaction mixture was concentrated

to a volume of B7 cm3 and slowly saturated with benzene by

the vapour diffusion method at ambient temperature until

colourless crystals were formed. The crystals were separated

by decantation and dried at 80 1C in vacuo to yield compound

rctt-4b (20.9 mg, 56%) as the 1 : 2 complex with KClO4;

mp > 310 1C (dec.) (Found: C, 50.58; H, 5.59. Calc.

for C60H80O20�2KClO4�1.5H2O: C, 50.56; H, 5.87%);

lmax(MeCN)/nm 281 and 235 (e/dm3 mol�1 cm�1 11 400 and

26 900); dH(500 MHz; DMSO-d6; 25 1C) 3.60 (16 H, m, 8 �CH2O), 3.66 (24 H, m, 8 � CH2O and 4 � 3-CH2CH2OAr),

3.75 (16 H, m, 4 � 4-CH2CH2OAr and 4 � 3-CH2OAr), 3.99

(8 H, m, 4 � 4-CH2OAr), 4.28 (4 H, s, 4 � CHAr), 6.37 (4 H,

br s, 4 � 2-H), 6.80 (4 H, d, J 8.2, 4 � 5-H) and 6.85 (4 H,

br d, J 8.2, 4 � 6-H); dC(125 MHz; DMSO-d6; 25 1C) 44.96

(4 � CHAr), 66.35 (4 � 4-CH2OAr), 66.46 (4 � 3-CH2OAr),

66.77 (4 � 3-CH2CH2OAr), 67.35 (4 � 4-CH2CH2OAr), 67.85

(4 � CH2O), 68.24 (4 � CH2O), 68.54 (4 � CH2O), 68.59

(4 � CH2O), 111.27 (4 � 5-C), 113.01 (4 � 2-C), 119.91

(4 � 6-C), 133.29 (4 � 1-C), 145.18 (4 � 4-C) and 146.54

(4 � 3-C); m/z (ESI MS) 583.2481 (calc. for C60H80O20�2Na+:

583.2519), 591.2345 (calc. for C60H80O20�Na+�K+: 591.2388),

599.2310 (calc. for C60H80O20�2K+: 599.2258), 1143.5127

(calc. for C60H80O20�Na+: 1143.5140) and 1159.4764 (calc.

for C60H80O20�K+: 1159.4880).

Cyclobutane rctt-4b, complex with Ca(ClO4)2. A solution of

a mixture of (E)-1b (41.4 mg, 73.9 mmol) and Ca(ClO4)2(19.4 mg, 81.3 mmol) in MeCN (15 cm3) was irradiated for

5 h according to the above described procedure. The reaction

mixture was concentrated to a volume of B10 cm3 and slowly

saturated with benzene–dioxane mixture (B2 : 1, v/v) by the

vapour diffusion method at ambient temperature until a

light-beige precipitate was formed. This precipitate was

recrystallized under the same conditions to give compound

rctt-4b (53.0 mg, 86%; impurity of rtct-4b o2 mol%) as the

1 : 2 complex with Ca(ClO4)2; mp >270 1C (dec.) (Found: C,

43.30; H, 4.91. Calc. for C60H80O20�2Ca(ClO4)2�3.5H2O: C,

43.35; H, 5.28%); lmax(MeCN)/nm 282 (e/dm3 mol�1 cm�1

10 400); dH(500 MHz; DMSO-d6; 28 1C) 3.57 (32 H, m,

16 � CH2O), 3.66 (8 H, m, 4 � 3-CH2CH2OAr), 3.70 (8 H,

m, 4 � 4-CH2CH2OAr), 3.87 (8 H, m, 4 � 3-CH2OAr), 3.93

(8 H, m, 4 � 4-CH2OAr), 4.26 (4 H, s, 4 � CHAr), 6.69 (4 H,

br s, 4 � 2-H), 6.71 (4 H, br d, J 8.2, 4 � 6-H) and 6.73 (4 H, d,

J 8.2, 4 � 5-H); dC(125 MHz; DMSO-d6; 26 1C) 46.31

(4 � CHAr), 68.32 (4 � 4-CH2OAr), 68.44 (4 � 3-CH2OAr),

68.65 (4 � 3-CH2CH2OAr), 68.81 (4 � 4-CH2CH2OAr), 69.74

(8 � CH2O), 70.27 (4 � CH2O), 70.33 (4 � CH2O), 113.25

(4� 5-C), 114.67 (4� 2-C), 120.43 (4� 6-C), 133.78 (4� 1-C),

146.68 (4 � 4-C) and 147.77 (4 � 3-C).

Cyclobutane rctt-4b. A solution of Me4NOH (20%, aq.)

(69 mcm3, 152.0 mmol) was added to a mixture of complex

rctt-4b�[Ca(ClO4)2]2�3.5H2O (39.3 mg, 23.6 mmol) and ethylene-

diaminetetraacetic acid (20.2 mg, 69.1 mmol) in water

(3 cm3). The resulting solution was thoroughly evaporated

in vacuo at 30 1C and the solid residue was extracted with

benzene (2� 20 cm3). The extracts were evaporated in vacuo to

yield free rctt-4b (24.3 mg, 92%) as a slightly yellowish

powder; mp 70–73 1C (Found: C, 64.23; H, 7.09. Calc. for

C60H80O20: C, 64.27; H, 7.19%); lmax(MeCN)/nm 284 and 232

(e/dm3 mol�1 cm�1 12 500 and 30 800); dH(500 MHz; DMSO-

d6; 26 1C) 3.57 (32 H, m, 16 � CH2O), 3.66 (8 H, m, 4 �3-CH2CH2OAr), 3.70 (8 H, m, 4 � 4-CH2CH2OAr), 3.87 (8 H,

m, 4� 3-CH2OAr), 3.93 (8 H, m, 4� 4-CH2OAr), 4.26 (4 H, s,

4� CHAr), 6.69 (4 H, br s, 4� 2-H), 6.71 (4 H, br d, J 8.2, 4�6-H) and 6.73 (4 H, d, J 8.2, 4 � 5-H); dC(125 MHz;

DMSO-d6; 26 1C) 46.31 (4 � CHAr), 68.30 (4 � 4-CH2OAr),

68.44 (4 � 3-CH2OAr), 68.64 (4 � 3-CH2CH2OAr), 68.79 (4 �4-CH2CH2OAr), 69.72 (8 � CH2O), 70.25 (4 � CH2O),

70.30 (4 � CH2O), 113.23 (4 � 5-C), 114.67 (4 � 2-C),

120.41 (4 � 6-C), 133.75 (4 � 1-C), 146.67 (4 � 4-C) and

147.76 (4 � 3-C).



2,3,5,6,8,9,11,12,14,15-decahydro-1,4,7,10,13,16-benzohexaoxa-

cyclooctadecine rctt-4c, complex with CsClO4. A solution of a

mixture of (E)-1c (20.3 mg, 31.3 mmol) and CsClO4 (7.7 mg,

32.9 mmol) in MeCN (15 cm3) was irradiated for 3 h according

to the above described procedure. The reaction mixture was

concentrated to a volume ofB5 cm3 and slowly saturated with

benzene by the vapour diffusion method at ambient temperature

until colourless druses were formed. These druses were separated

by decantation and dried at 80 1C in vacuo to yield compound

rctt-4c (21.2 mg, 73%) as the 1 : 2 complex with CsClO4; mp

222–224 1C (Found: C, 46.57; H, 5.61. Calc. for C68H96O24�2CsClO4�0.15C6H6: C, 46.65; H, 5.51%); lmax(MeCN)/nm

281 and 235 (e/dm3 mol�1 cm�1 14 700 and 35 200);

dH(500 MHz; DMSO-d6; 30 1C) 3.55–3.62 (40 H, m,

20 � CH2O), 3.65 (16 H, m, 8 � CH2O), 3.68–3.78 (16 H,

m, 4 � 4-CH2CH2OAr and 4 � 3-CH2OAr), 4.03 (8 H, m, 4 �4-CH2OAr), 4.27 (4 H, s, 4� CHAr), 6.27 (4 H, br s, 4� 2-H),

6.84 (4 H, d, J 8.3, 4 � 5-H) and 6.89 (4 H, br d, J 8.3, 4 �6-H); dC(125 MHz; DMSO-d6; 26 1C) 44.37 (4� CHAr), 66.18

(4 � 4-CH2OAr), 66.62 (4 � 3-CH2OAr), 67.54 (4 � CH2O),

67.74 (4� CH2O), 68.46 (4� CH2O), 68.89 (4� CH2O), 69.05

(8 � CH2O), 69.27 (4 � CH2O), 69.55 (4 � CH2O), 110.34

(4� 5-C), 112.41 (4� 2-C), 119.40 (4� 6-C), 132.51 (4� 1-C),

144.99 (4 � 4-C) and 146.29 (4 � 3-C); m/z (ESI MS) 347.1417

(calc. for C68H96O24�4Na+: 347.1471), 455.1924 (calc. for

C68H96O24�3Na+: 455.1995), 671.2965 (calc. for C68H96O24�2Na+: 671.3044) and 679.2836 (calc. for C68H96O24�Na+�K+: 679.2913).

Cyclobutane rctt-4c, complex with salt C3. A solution of a

mixture of (E)-1c (40.1 mg, 61.9 mmol) and 1,3-propanedi-

ammonium diperchlorate (C3) (18.7 mg, 68.1 mmol) in MeCN

(15 cm3) was irradiated for 4 h according to the above

described procedure. The reaction mixture was concentrated

to a volume of B10 cm3 and slowly saturated with benzene by

the vapour diffusion method at ambient temperature until a

slightly yellowish amorphous precipitate was formed. This

precipitate was separated by decantation and dried at 80 1C

in vacuo to yield compound rctt-4c (42.6 mg, 75%) as the 1 : 2

complex with C3; mp 192–195 1C (Found: C, 48.04; H,

6.61; N, 2.95. Calc. for C68H96O24�2C3H12Cl2N2O8: C, 48.11;

H, 6.55; N, 3.03%); lmax(MeCN)/nm 280 and 231

(e/dm3 mol�1 cm�1 17 700 and 43 900); dH(500 MHz;

DMSO-d6; 26 1C) 1.79 (4 H, m, 2 � CH2CH2NH3), 2.85 (8

H, m, 4� CH2NH3), 3.51 (16 H, m, 8� CH2O), 3.54 (16 H, m,

8 � CH2O), 3.57 (16 H, m, 8 � CH2O), 3.65 (8 H, m,

4 � 3-CH2CH2OAr), 3.69 (8 H, m, 4 � 4-CH2CH2OAr),

3.91 (8 H, m, 4 � 3-CH2OAr), 3.95 (8 H, m, 4 � 4-CH2OAr),

4.26 (4 H, s, 4 � CHAr), 6.696 (4 H, br d, J 8.6, 4 � 6-H),

6.703 (4 H, br s, 4 � 2-H), 6.74 (4 H, d, J 8.6, 4 � 5-H) and

7.67 (12 H, br s, 4 � NH3).

Cyclobutane rctt-4c. A dispersion of complex rctt-4c�(C3)2(35.1 mg, 19.0 mmol) or rctt-4c�(C4)29 (46.0 mg, 24.5 mmol) in

water (20–30 cm3) was extracted with a mixture of benzene

(25–30 cm3) and CH2Cl2 (10–15 cm3). The organic extract was

evaporated in vacuo to yield free rctt-4c [15.8 mg, yield 64% in

the case of rctt-4c�(C3)2 or 27.7 mg, yield 87% in the case of

rctt-4c�(C4)2] as a slightly yellowish viscous oil; lmax(MeCN)/

nm 283 and 232 (e/dm3 mol�1 cm�1 14 800 and 33 000);

dH(500 MHz; DMSO-d6; 26 1C) 3.52 (16 H, s, 8 � CH2O),

3.54 (16 H, m, 8 � CH2O), 3.58 (16 H, m, 8 � CH2O), 3.66

(8 H, m, 4 � 3-CH2CH2OAr), 3.70 (8 H, m, 4 �4-CH2CH2OAr), 3.91 (8 H, m, 4 � 3-CH2OAr), 3.96 (8 H,

m, 4 � 4-CH2OAr), 4.27 (4 H, s, 4 � CHAr), 6.70 (4 H, br d,

J 8.2, 4 � 6-H), 6.71 (4 H, br s, 4 � 2-H) and 6.75 (4 H, d,

J 8.2, 4 � 5-H); dC(125 MHz; DMSO-d6; 26 1C) 46.42 (4 �CHAr), 68.02 (4 � 4-CH2OAr), 68.08 (4 � 3-CH2OAr), 68.61

(4 � 3-CH2CH2OAr), 68.76 (4 � 4-CH2CH2OAr), 69.77 (24 �CH2O), 112.69 (4 � 5-C), 114.06 (4 � 2-C), 120.21 (4 � 6-C),

133.60 (4 � 1-C), 146.34 (4 � 4-C) and 147.40 (4 � 3-C).

1H NMR titration

The titration experiments were performed in MeCN-d3 (the

water content r0.05%, FGUP RNTs Prikladnaya Khimiya,

St. Petersburg, Russian Federation) or MeCN-d3–D2O

(10 : 1, v/v) solutions at 30 � 1 1C. The concentration of

(E)-1a–c, B15C5 was maintained at about (1, 2, or 5) � 10�3 M

depending on solubility of the components and/or complexes.

The concentration of metal perchlorate or C3 in the solution

was gradually increased starting from zero. The highest salt/

1(B15C5) concentration ratios were about 3–5. The proton

chemical shifts were measured as a function of the salt/

1(B15C5) ratio. The DdH values were measured with an

accuracy of 0.001 ppm and then the complex formation

constants were calculated using the HYPNMR program.21

In the case of log K1:1 >5, the values of log K2:2 and/or

log K1:2 were determined taking into account a fixed rough

value for log K1:1 which was chosen by the criterion of minimal

rms weighted residuals.

X-Ray crystallography

The crystals of complexes of stilbenes (E)-1b,c and cyclo-

butane rctt-4b were grown as described above. The single

crystals of all compounds were coated with perfluorinated

oil and mounted on a Bruker SMART-CCD diffractometer

[graphite monochromatized Mo-Ka radiation (l= 0.71073 A)

or Cu-Ka radiation (l = 1.54178 A), o scan mode] under

a stream of cold nitrogen (T = 120.0(2) or 100(2) K,

respectively). The sets of experimental reflections were

measured and the structures were solved by direct methods

and refined with anisotropic thermal parameters for all non-

hydrogen atoms (except for the strongly disordered picrate

anion and benzene molecule in structure 1c�CsPic�C6H6 and one

of independent benzene molecules in structure 1c�C3�2.67C6H6,

which were refined isotropically). In some cases, absorption

correction was applied using the SADABS method. The

hydrogen atoms were fixed at calculated positions at carbon

atoms and then refined with an isotropic approximation for

1b�2Ca(ClO4)2�2MeCN�4H2O or using a riding model for

other structures. The hydrogen atoms of the NH3+ group in

structure 1c�C3�2.67C6H6 were calculated geometrically and

refined using a riding model. Hydrogen atoms of the solvation

water molecules in structure 1b�2Ca(ClO4)2�2MeCN�4H2O

were located from the difference Fourier map and refined


isotropically. In other hydrated structures, hydrogen atoms of

the water molecules were not located.

Crystal data for 1b�2NaClO4: C30H40Cl2Na2O18,M= 805.50,

monoclinic, a = 26.083(2), b = 9.2443(9), c = 15.8150(13) A,

b = 96.659(5)1, V= 3787.5(6) A3, space group P21/c (no. 14),

Z = 4, m = 0.269 mm�1, 45 379 reflections measured, 9987

unique (Rint = 0.5344) which were used in all calculations. The

final R1 and wR2 were 0.2426 and 0.3541 (for 3733 reflections

with I > 2s(I)), 0.4133 and 0.4098 (for all data). The ISOR

command was applied for the most non-hydrogen atoms. The

experiment was collected from a weakly reflected crystal. For

this reason, the final parameters are characterized by low

accuracy. Unfortunately, we failed to obtain better crystals

and better structural data. Nevertheless, we included this

structure in this article without a discussion of thin details of

the geometry just in order to show one more type of coordination

mode of 1b to a metal cation.

Crystal data for 1b�2Ca(ClO4)2�2MeCN�4H2O:

C34H54Ca2Cl4N2O30, M = 1192.75, monoclinic, a = 8.1196(2),

b = 16.2587(5), c = 19.1065(5) A, b = 97.303(1)1, V =

2501.84(12) A3, space group P21/n (no. 14), Z = 2,

m = 0.538 mm�1, 17 932 reflections measured, 6562 unique

(Rint = 0.0164) which were used in all calculations. The final

R1 and wR2 were 0.0345 and 0.0898 (for 6044 reflections with

I > 2s(I)), 0.0378 and 0.0940 (for all data). The both

independent perchlorate anions are disordered over two

positions with occupancies 0.62 : 0.38 and 0.70 : 0.30. The ISOR

command was applied for atom O(25) of anion Cl(2)O4�.

Crystal data for 1b�KPic�C6H6: C42H48KN3O17,

M = 905.93, triclinic, a = 12.3927(10), b = 13.7956(11),

c = 14.7748(12) A, a = 104.967(4), b = 108.561(4), g =

105.014(4)1, V= 2146.7(3) A3, space group P�1 (no. 2), Z= 2,

m = 0.203 mm�1, 15 990 reflections measured, 10 796 unique


R1 and wR2 were 0.1104 and 0.2224 (for 4212 reflections with

I > 2s(I)), 0.2583 and 0.2690 (for all data). The solvate

benzene molecule is disordered over two positions with

occupancies 0.63 : 0.37. The ISOR command was applied

for all carbon atoms of the disordered benzene molecule.

Crystal data for 1c�CsPic�C6H6: C46H56CsN3O19,

M = 1087.85, triclinic, a = 12.7413(3), b = 17.2121(4), c =

23.8339(5) A, a = 83.200(1), b = 80.486(1), g = 70.437(1)1,

V = 4846.22(19) A3, space group P1 (no. 2), Z = 4, m =

0.844 mm�1, 62 607 reflections measured, 25 689 unique


R1 and wR2 were 0.0808 and 0.2017 (for 11 775 reflections with

I > 2s(I)), 0.1801 and 0.2340 (for all data). Many of

independent components of the crystal cell are strongly disordered

(see a detailed description in the corresponding CIF file

available from the CCDC) and because we needed to apply

a number of the SADI, FLAT, and ISOR commands to

constrain their geometric and anisotropic parameters.

Crystal data for 1c�C3�2.67C6H6: C53H76Cl2N2O20,

M = 1132.06, trigonal, a = b = 21.0741(3), c = 33.4590(6) A,

V = 12868.9(3) A3, space group R32 (no. 155), Z = 9,

m = 1.659 mm�1 (for Cu-Ka radiation), 14 469 reflections

measured, 4708 unique (Rint = 0.0421) which were used in all

calculations. The final R1 and wR2 were 0.0628 and 0.1753 (for

4541 reflections with I > 2s(I)), 0.0647 and 0.1790 (for all

data). Molecule 1c reveals a complicated disorder in crystal

(see Fig. S1a, ESIw). Three crystallographically independent

perchlorate anions are also disordered: they occupy two

different positions with symmetry 3222 and special position

in 2-fold axis. One solvate benzene molecule reveals rotation

disorder in its plane over two positions with occupancies

0.66 : 0.34, whereas, the second benzene molecule is situated

in 3-fold axis. The SADI and ISOR commands were applied

to some atoms of the disordered perchlorate anions and

bis(18-crown-6)stilbene molecule. In this X-ray experiment,

5 ClO4� anions per 3 propanediammonium ions have been

found, although 2 anions per organic dication are required for

electrical neutrality of compound C3. This discrepancy may

only be eliminated if the formula unit H3N+(CH2)3NH3

+ is

partly statistically deprotonated. On the other hand, elemental

analysis data for this complex agree well with complete

protonation of this species (see above). We cannot explain

this disagreement now. We only note that all crystal space is

filled completely and no residual electron density peaks higher

than 0.43 e A�3 that could be assigned as the additional ClO4–

anion occur.

Crystal data for rctt-4b�2KClO4�2C6H6�4H2O:

C72H100Cl2K2O32, M = 1626.62, monoclinic, a = 13.9879(9),

b = 26.9584(19), c = 21.0031(15) A, b = 103.011(4)1, V =

7716.8(9) A3, space groupC2/c (no. 15),Z=4, m=0.279 mm–1,

43 634 reflections measured, 10 251 unique (Rint = 0.1790)

which were used in all calculations. The final R1 and wR2 were

0.1020 and 0.2778 (for 4619 reflections with I > 2s(I)), 0.2154and 0.3110 (for all data). Three of four independent solvate

water molecules have incomplete position occupancies. The

ISOR command was applied to 6 atoms.

Crystal data for rctt-4b�2Ca(ClO4)2�3C6H6�9H2O:

C78H116Ca2Cl4O45, M = 1995.67, triclinic, a = 14.4368(8),

b = 17.9290(11), c = 18.9170(11) A, a = 78.740(3), b =

84.002(3), g = 87.880(3)1, V = 4775.2(5) A3, space group P�1

(no. 2), Z = 2, m = 0.324 mm–1, 46 792 reflections measured,

25054 unique (Rint = 0.2700) which were used in all calculations.

The final R1 and wR2 were 0.1145 and 0.2320 (for 5685

reflections with I > 2s(I)), 0.3780 and 0.2961 (for all data).

One of five independent perchlorate anions, Cl(3)O4�, is

disordered over two positions with occupancies 0.77 : 0.23.

Anions Cl(4)O4� and Cl(5)O4

� have occupancies of 0.61 and

0.39, respectively. Some of the eleven solvate water molecules

have incomplete occupancies. The ISOR command was

applied to some non-hydrogen atoms.

All the calculations were performed using the SHELXTL-

Plus software.22 CCDC reference numbers 780037

(1b�2NaClO4), 780035 [1b�2Ca(ClO4)2�2MeCN�4H2O],

780036 (1b�KPic�C6H6), 780039 (1c�CsPic�C6H6), 780038

(1c�C3�2.67C6H6), 780041 (rctt-4b�2KClO4�2C6H6�4H2O),

and 780040 [rctt-4b�2Ca(ClO4)2�3C6H6�9H2O].

Acknowledgements

Support from the Russian Foundation for Basic Research, the

Russian Academy of Sciences, the Royal Society (L.G.K.),

and the Engineering and Physical Sciences Research Council

(EPSRC) for a Senior Research Fellowship (J.A.K.H.) is

gratefully acknowledged.


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